Plasma Spray Synthesis of High Purity Boron Nitride Nanotubes

The objective of this project is the efficient synthesis of high quality boron nitride nanotubes (BNNT’s) using the LaRC radio frequency plasma spray (RFPS) facility.  Efficient synthesis implies large quantities via a reliable and readily-scalable process.  High quality infers a product of high purity with an abundance of defect-free, small diameter nanotubes.

Compared with carbon nanotubes, BNNT's possess better mechanical properties and are thermally stable to much higher temperatures. The potential benefits of BNNT-reinforced structural materials can only be explored if commercial quantities of high purity, low defect BNNT's are available to the aerospace industry. The majority of nanotube production for structural composires is focused on generating 'yarn' for continuous reinforcement of polymer-based matrices.  The goal of this effort is to synthesize relatively short 'fibers' for discontinuous reinforcement of metal- or ceramic-based matrices.

A novel combination of the RFPS process with a chemical reaction chamber for rapid, in-situ synthesis is envisioned.  The effort will draw on extensive work performed in Russia during the 1980's (Tumanov, et al.).  Their nuclear industry developed 'plasma-chemical synthesis' of nano-sized powders of metal oxides, carbides and nitrides.  The lack of consumable electrodes and the confined environment characteristic of RFPS offer big advantages over the DC and atmospheric plasma techniques employed in the prior work.  It is anticipated that the approach will yield abundant quantities of high purity nanotubes of the order of 10 microns long.  A goal will be to separate single- and multi-walled species during the process.